Evaluation of thermal conductivity for thermally insulated concretes

Passive energy-saving houses and buildings made of thermally insulated materials become popular in recent construction practices to address the demanding energy needs and to reduce the consumption of hydrocarbon energy resources. Thermally insulated concretes represent alternative construction materials to improve the thermal efficiency in a wide range of residential and commercial buildings. This study presents the experimental results of thermal conductivity values of lightweight concrete materials at ambient temperature conditions. Various lightweight aggregates and glass bubbles are selected as surrogates and replacement materials for coarse aggregates in order to reduce the thermal conduction in concretes. The linear and plane heat source methods are implemented to quantitatively obtain conductivity values for tested specimens. Results highlight that the thermal conductivity of concretes can be effectively reduced with increasing fraction of lightweight aggregates critically depending on the type of lightweight aggregates, thereby playing an important role in the thermal insulation. The addition of micro-meter sized hollow glass bubbles further decreases the thermal conductivity of specimens while its impact is less pronounced than the lightweight aggregates. The measurement of strength corroborates the soundness of mechanical applicability of tested concretes specimens as well.